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Re: [Xen-devel] [PATCH v10] x86/altp2m: support for setting restrictions for an array of pages


  • To: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>, Wei Liu <wei.liu2@xxxxxxxxxx>, Petre Pircalabu <ppircalabu@xxxxxxxxxxxxxxx>
  • From: George Dunlap <george.dunlap@xxxxxxxxxx>
  • Date: Fri, 30 Mar 2018 11:03:45 +0100
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  • Cc: tim@xxxxxxx, sstabellini@xxxxxxxxxx, George.Dunlap@xxxxxxxxxxxxx, andrew.cooper3@xxxxxxxxxx, ian.jackson@xxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxx, jbeulich@xxxxxxxx
  • Delivery-date: Fri, 30 Mar 2018 10:04:04 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Openpgp: preference=signencrypt

On 03/30/2018 07:34 AM, Razvan Cojocaru wrote:
> On 03/13/2018 07:44 PM, Wei Liu wrote:
>> On Wed, Dec 13, 2017 at 04:22:20PM +0200, Petre Pircalabu wrote:
>> [...]
>> Tabs here.
>>
>> With this fixed, libxc bits:
>>
>> Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> 
> We seem to have (again) arrived at an impasse with this patch.
> 
> To summarize, the original designers of altp2m have not replied anything
> to repeated requests for comments, we've briefly discussed the issue at
> the Xen Developer Summit last year, and it was concluded that, since we
> do have a valid use case, we carry on with whatever design most fit with
> the single-page setting xc_altp2m_set_mem_access() (which is a HVMOP).
> 
> Previously, Andrew has argued for the operation to be a HVMOP (in
> keeping with the original design), while Jan has pointed out that since
> this is only currently useful as a DOMCTL it would perhaps better be
> implemented as one (which I personally also prefer, as it gets rid of
> the very ugly compat code).
> 
> In the process of negotiating this, concerns have been voiced about the
> possibility of restricting altp2m operations from either dom0 or the
> guest. This is addressed, IMHO, by Tamas' patches:
> 
> https://patchwork.kernel.org/patch/9661873/
> 
> The situation is now this: Wei's obviously acked it; Jan agrees to let
> it in, pending acks from Andrew or George.
> 
> We're happy to address any clear objections. But it would be a shame to
> lose all this work we've all been doing for the better part of an year,
> as I'm sure we all agree.
> 
> Please let us know how to proceed.

Hey Razvan,

Not sure if you were on the list for the x86 community call, but this
probably would have been a good item to put on the agenda to discuss
last month -- the purpose of the call is to try to work through just
these sorts of impasse.

In response to v8, I said:  "FWIW the approach looks good to me here.
You mainly need an x86 maintainer's ack and a toolstack maintainer's
ack (of which I am neither)."

I'm not a maintainer of `xen/arch/x86/hvm/hvm.c` -- that's Andy and Jan.

OTOH, altp2m is a p2m feature, so arguably it should be primarily my
responsibility.

Anyway, I'll take a look at it today; if I can give a Reviewed-by, then
maybe we can negotiate for it to go in with just that (with my committer
hat on on), or for Andy to Ack it based mostly on my R-b.

 -George


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